In many field of electronics, it is often necessary to select and to eliminate signal of a frequency band. YIG type tunable filters are available.
Ferroelectric materials have a number of attractive properties. Ferroelectrics can handle high peak power. The average power handling capacity is governed by the dielectric loss of the material. They have low switching time (such as 100 nS). Some ferroelectrics have low losses. The permittivity of ferroelectrics is generally large, as such, the device is small in size. The ferroelectrics are operated in the paraelectric phase, i.e. slightly above the Curie temperature. Inherently they have a broad bandwidth. They have no low frequency limitation as in the case of ferrite devices. The high frequency operation is governed by the relaxation frequency, such as 95 GHz for strontium titanate, of the ferroelectric material. The loss of a ferroelectric tunable filter is low with ferroelectric materials with a low loss tangent. A number of ferroelectric materials are not subject to burnout.
Das discussed the properties of ferroelectric microstrip phase shifters for a two element array. S. Das, "Ferroelectrics for Time Delay Steering of an Array", Ferroelectrics, vol. 5, No. 3/4, 1973.
Depending on trade-off studies in individual cases, the best type of filter can be selected.